Designing for Efficiency

Operation Considerations

Operation Time
Key 0.2s
Mouse Point 1.1s
Homing 0.4s

Times based on GOMS Keystroke Model, presented in The Psychology of Human-Computer Intearction by Card, Moran and Newell.

Other considerations

  • Scanning a list (250ms per item) for first-time user
  • Practiced pointing in a list
  • Tablet reported to have approximately 0.4 keystroke time

Relevant principles

  • Fitts's law --- pointing time is a log function of distance / size
  • Hick-Hyman law --- selection time is a log function of the number of items (see Figure 1 in Cockburn et al.)